Parts, products, and other objects are often rendered with computer-aided design (CAD) models before they are manufactured. These models are often used to produce the objects with additive manufacturing (AM) technologies. Typically, three-dimensional models in the form of triangulated stereolithography (STL) files must be created with CAD software to control the laying down of successive layers of materials to create three-dimensional objects. The STL files are composed of triangles that represent objects' bounding surfaces. Before an STL file can be used it must be checked for errors such as unintentional holes, inconsistent face-normal directions, self-intersections, noise shells, and manifold errors. Once finished, the STL file is processed by “slicer” software which converts the CAD model into a series of offset two-dimensional profiles, called “slices”.
The slicing plane is typically defined with two or three points by specifying a major plane of the user coordinate system (UCS), or by selecting a planar or a surface object, but not a mesh. Sliced objects retain the layer and, in some instances, color properties of the original CAD objects, however the resulting surface or slice objects do not retain a history of the original CAD objects. Thus, the CAD model is converted into a triangulated surface mesh, the intersection of each triangle with the desired build-slice plane is determined, resulting in a single line segment per intersected triangle, which together establish the boundaries which describe the region to build. The resulting “slice file” describes each layer of the object to be built.
This current method is not robust or efficient for objects that have fully-defined native CAD models. “Auto” generation of triangle meshes used by most CAD and AM tools produce low quality meshes which may have thousands of errors which adversely affect the AM process. Further, when a CAD model with non-linear features is approximated by linear triangles it is no longer possible to refine the linear surface mesh to increase accuracy, and the original CAD file must be re-meshed with finer resolution. Even options like the Additive Manufacturing File format, defined in ASTM 52915, fail to accurately represent all curved surfaces because these formats may not use the same basis functions to define curvature as does the native CAD model. Additionally, some techniques involve slicing “on the fly”, i.e., while printing the object. However, converting to and fixing triangles prior to slicing is time-consuming and can require an hour or more of time between printing successive layers, which significantly slows the AM process, and if the slice file encounters a problem, the AM process may need to be aborted and the material already expended may be wasted.
This background discussion is intended to provide information related to the present invention which is not necessarily prior art.